Contactor base for lamps, tubes, and the like



Dec. 20, 1938.

R. M. ZABEL CONTACTOR BASE FOR LAMPS, TUBES, AND THE LIKE F il'ed Sept. 17; 1935 2 Sheets-Sheet 1 INVENTOR BYfi/za 1 ATTORNEY R. M. ZABEL Dec. 20, 1938.

GONTACTOR BAS E FOR LAMPS,- TUBES, AND THE LIKE Filed Sept. 17, 1955 2 Sheats-Shqet 2 |NVENTOR ATTORNEY Patented Dec. 20, 1938 umrso STATES CONTAUIOR BASE FOR LAMPS, TUBES,

Rolland M. Zabel, Lynnfield, Mass, assignor to Hygrade Sylvania Corporation, corporation of Massachusetts Salem, Mass.,'a

Application'September 17, 1935, Serial No. 40,871

f 7 Claims.

This invention relates to contactor bases and more particularly to bases for electric lamps, radio tubes and similar devices.

An object of the invention is to provide an improved base structure for electric lamps and the like, wherein the possibility of destructive arcing in the base is reduced to a minimum, particularly when a protective fuse is incorporated within the base.

In the ordinary electric lamp of the incandescent type, the base consists of a threaded, hollow metal shell affixed at one end to the lamp bulb, and at the other end to an insulating plug bearing an eyelet contact button. One'of the lead-in wires to the base may include a fuse wire to protect the lamp against arcing in the bulb at burnout, as shown for example in copending application, Serial No. 416, filed January 4, 1935. On blowing of the fuse, however, a destructive arc may occur to the exposed surface ofthe shell or eyelet.

Accordingly one of the principal objects of this invention is to provide an electric lamp, radio tube or the like with a fuse lead-in wire having a specially insulated base whereby the creation or maintenance of a destructive arc between the lead-in wires and base is substantially entirely avoided.

Another object of the invention is to provide an electric lamp with a fuse lead-in wire and a metal shell base having a contact button insulatingly attached to the base, the fuse lead-in wire being conductively connected to the shell which has its inner surface effectively shielded from the other lead-in wire.

Another object of the invention is to provide an electric lamp with a fuse lead-in wire and a metal shell base having the usual eyeleted contact button, the fuse lead-in wire being conductively connected to the button and with the eyelet eifectively insulated from the inner surface of the shell. 1

A feature of the invention relates to an electric lamp, radio tube or the like having a shell type base cemented to the bulb and with one or both of the lead-in wires designed to act as a protective fuse and directly imbedded in the cement, which is preferably chosen of a suitable.

insulating material of sufiflcient porosity to prevent the maintenance of a' destructive are within the base when the fuse blows.

- Other features and advantages not specifically enumerated will be apparent after a consideration of the following descriptions and the appended claims.

Inasmuch as the present invention is concerned mainly with the manner of providing lamps, tubes and the like with contactor 'bases, only those parts of a lamp or tube are shown which are necessary to an understanding of the inven- 5 tive concept, and like parts throughout the several figures of the drawings are referred to by the same designation numerals.

Fig. 1 is a crossrsectional view of a lamp having a base constructed according to the invention.

Fig. 2 shows a mo Fig. 1.

Fig. 3 shows the inventive concept embodied in a mechanically based lamp.

Fig. 4 shows a modified manner of insulating the interior of a lamp base according to the infication of the structure of vention.

path interiorly of the shell either between the eyelet and the inner wall of the shell or between 30 one of the lead-in wires and the shell or eyelet. This is particularly true when one of the lead-in wires has a portion of its length constituted of fuse material. I have found that with the ordinary base structure when the fuse blows, the released gases and metal particles of the arc not only may strike an are within the shell, but that this are may continue until either the shell or the eyelet is punctured and the are then destroys the fixture within which the lamp is mounted. I have found that in order to protect the lamp as well as the fixture it is not only necessary to employ a fuse lead-in wire but also to make certain that the particular contact of the base to which the fuse lead-in connects, is effectively insulated or shielded from the resultant are when the. fuse blows. If this is not done the fuse will continue to melt until the are eventually reaches the contact proper under which condition the blowing of the fuse becomes destructive rather than protective. I have also found that it is advisable to imbed the fuse lead-in preferably directly in an insulating material which is particularly designed to facilitate extinction of the fuse are before it can reach the contact to which so the fuse lead-in is connected. One of the materials that has been found useful for this latter purpose is a cement which has the property when heat treated or. cured of bondingitself to glass and metal, but which in its uncured state is sufficiently soft to allow the, lead-in wire to be imbedded therein or passed therethrough with the ordinary procedure such as is employed in automatic basing machines.

Referring to Fig. 1 of the drawings there is shown a based lamp or tube embodying features whereby the parts of the lamp such as the glass bulb and also the shell base, are protected. In

' this figure the lead-in wire 5 has any desired part of its length formed of a fuse wire i2 which may be united to the portion 5 in any well-known for purposes to be described. The insulating plug it may be of glass, Bakelite or other suitable insulating material. The metal shell with the extended insulator skirt is then provided adjacent its rim with'a ring of cement M which in its normal or uncured state is semi-plastic. One kind of cement that has been found useful for the purposes of this invention is composed as follows:

In applying the ring of cement it is important that just the right quantity is used to effect the insulating of the inner face of the shell. It is the customary practice in applying the base to the bulb to invert the base as indicated for example in Fig. 5, and to move the lamp bulb and base in a vertical direction with relation to each other until the end of the bulb is seated against the rim of the shell base. Prior to this however the fused lead-in wire I2 is bent back upon itself in a loop as shown in Fig. 1 so that when the bulb and base are brought together the leadin wire I! imbeds itself in the cement ring l4 and protrudes outwardly beyond the. rim of the base to which it may be soldered'or otherwise fastened. At this time also, the lead-in wire 4 is passed through the eyelet l0 and may be soldered to the button ll. When the bulb and base have been properly assembled the cement ring I4 is subjected to a heating or curing treatment as a result of which it hardens to a somewhat porous mass and bonds itself to the rim of the Shell 8, to the wire I2 and also to the bottom of the bulb. Preferably the cement ring is cured in such a manner that while it becomes porous,

during the usual basing operation may cause thealcohol to be released in sufficient quantity and velocity as to form one or more pores of sum-- ciently large size to permit the passage of a destructive arc. Thus after the ring of cement has been applied, the base may be stored at room temperature for three to five days and then the base may be applied to the lamp in accordance with the usual basing operation to effect the complete curing thereof.

As will be noted from the drawings, the cement ring is applied in just suflicient quantity so that when the bulb and shell are pressed together during assembly of the base, the cement flows into contact with the rim l6 of the glass skirt and efiects the shielding of the inner face of the shell. If it were attempted to employ the usual short skirt glass plug, the fluidity of the cement and its subjection to pressure during the assembly'of the base and bulb might cause the cement to fall away from the shell, resulting in an appreciable unshielded area on the inner face of the shell. For this reason therefore it is preferred to extend the skirt ll beyond the middle of the shell so as to insure the cement forming a continuation of the skirt. With this type of base, should the fuse portion 12 blow for any reason, the fuse melts very rapidly; however since the inner face'of the shell 8 is effectively protected, the only waythe cfurrent can flow is through the remainder of the fuse which is imbedded in the cement I4. Because of the porosity or spongy character of the cement, the arc is extinguished therein before it has an opportunity of reaching the shell 8. I have found that the type of cement above described possesses the property of extinguishing the are before it can become destructive and while I do not wish to be restricted to any particular theory for this action I believe it is due to the fact that the porous or nonaligned cellularstructure of the cement creates sufficient deionization area for the metal particles and ionized gases of the arc, so that the arc cannot follow the previous path of the fuse. It will be understood that the invention is not limited to any particular proportion of lengths between the glass skirt l1 and thecement ring I t, so long as both these elements contact with each other to provide a tubular-like shield for effectively protecting theinner surface of the shell,. which shield is in intimate contact with the inner surface of the shell. 1

Instead of employing an extended skirt IT, a shorter skirt may be employed as indicated in Fig. 2 by the numeral Hi. In this embodiment the completion of the shielding between the skirt. "3 and the cement ring l4 iseifected by means of a separate insulating sheath I9 which may be of any suitable insulating material or may be in the form of a coating of insulating paint or varnish on the inner face of the shell 8. The sheath fused lead-in wire 4 and from the eyelet III.

In the-foregoing embodiments the lamp or bulb is of the so-called cement-based type, that is wherein the bulb is fastened to the shell base by the cement ring described. In applying the invention to so-called mechanically-based lamps or bulbs, the procedure must be mochfied. Thus in one particular type of mechanically based lamp, the baseconsists of two separate threaded metal members which must be capable of relative turning movement in the assembly thereof. Accordingly the arrangement of Figs. 1 and 2 is not applicable to this type of base and it becomes necessary to bring the fused lead-in wire to the eyeshell base.

- 2,141,148 let instead of to the shell. Here again I have found that it is necessary to effectively protect the eyelet from the plain lead-in and from the As indicated in Fig. 3 the bulb may be of the type having a cylindrical neck 20 sealed to the reentrant stem 2, the sea] area preferably being molded to a reduced cylindrical shape as shown and also being provided with a series of circular recesses 2! to receive corresponding embossed projections 22 on the threaded tubular metal member 23 whereby this latter member is prevented from turning relatively to the bulb. Threaded on to the member 23 is a correspondingly threaded metal shell 24 which has struckup portions engaging corresponding openings in member 23 to couple the shell and member 23 together. The plain lead-in wire is soldered or otherwise connected to the member 23 while the fuse lead-in wire has its fuse portion i2 brought out through the eyelet Ill in the metal contact button I l it being understood that the button II is bonded to the glass plug 26 which in turn is bonded to-the shell 24. In accordance with the invention, prior to passing the fuse lead-in wire l2 through the eyelet ID, the recess in the plug 26 is filled with a cement 21 of the character described above in connection with Figs. 1 and 2. As pointed out, the cement 21 in its uncured state is semi-plastic and it is possible without any difficulty to pass the lead-in wire l2 therethrough and through the eyelet l0. Thereafter the cement filling is cured preferably so that when it hardens it forms a somewhat porous or spongy structure wherein the cellular spaces are sufficiently small and are non-aligned to provide deionization areas as above described, while effectively insulating the eyelet In from the plain lead-in wire 4 and from the interior surface of the members 23 and 24. Thus the cement may ing of the cement may be achieved when the 'base is applied to the lamp by the usual basing method during which the cement is raised to a relatively high curing temperature for a few minutes. Should the fuse I 2 blow, the character of the cement 21 prevents the are from followingthe previous path of the fuse, and thus prevents the arc vapors, and metallic particles from forming a conductive path to the eyelet l and thence to the socket or fixture in which the lamp is inserted.

Referring to Figs. 4, 5, and 6 there is shown a modification of the structure of Figs. 1 and 2. In this embodiment the threaded metal shell 8 is provided with the usual low skirt glass plug 28 carrying the metal contact button I I. The major part of the inner surface of the shell 8 is provided with a coating 29 of a cement preferably of the same composition as that described hereinabove. The cement coat 29 is however heated or cured to render it had prior to assembling the lamp bulb in the base and prior to applying the cement'ring I. For this purpose the cement 29 may be heated to approximately 50 degrees centigrade for about three days although it will be understood that the invention is not limited to curing operation by drying out at room temperar ture for a few days after which the base may be applied to the lamp in accordance with the usual basing operation. The base is inverted as shown in Fig. and the lamp bulb I is assembled in place, with the fuse lead-in wire l2 bent back upon itself with its end protruding beyond the rim of the shell. The assembled base is then heated to cure the cement it which hardens to form a somewhat porous mass in which the fused lead-in wire is directly imbedded.

It will be understood of course that the invention is not limited to any particular length of fuse. Thus the fuse portion of the lead-in wire may have its complete length imbedded within the insulating arc-suppressing means, or if desired the fuse may have an imbedded portion as well as a portion extending beyond the insulating means.- In the case where the fuse has its entire length imbedded the fuse length should be suflicient toprovide the necessary protection after the blowing thereof. Furthermore while the drawing shows only one of the lead-in wires provided with a fuse portion it will be understood that both lead-in wires may be provided with fuse portions, however inthis latter case it is not necessary that both the fuse lead-in wires be imbedded within the insulating material, al-

though it may be desirable in certain cases to I have both fuse l ad-in wires imbedded in the insulating means. V

This application is a continuation-in-part'of application Serial No. 750,473, filed October 29th,

1934 and application Serial No. 416, filed January 4th, 1935, which was issued August 24, 1937, as United States Patent No. 2,091,233.

What is claimed is;

1. In combination, an electric lamp bulb, a hollow cylindrical metal shell serving as one contact of a contact base and afiixed to the lamp bulb by a ring of porous, insulating arc-quenching cement near the rim of the shell, a fuse wirepassing through said ring of cement and electrically connected to said shell and to a lamp bulb lead-in wire, part of the length of said fuse wire being directly embedded in the cement through which it passes and another part being exposed to the atmosphere inside the base, a second lead-in wire to said lamp bulb and elec trically connected to a contact button supported by an insulating plug which closes off the end of the metal shell farthest from the lamp bulb, and

an insulating ring which bridges the space base by all paths except through the fuse.

2. The combination of claim 1, in which the insulatlng ring which bridges the space between the said cement ring and the insulating plug isa second ring of .cement.

3. In combination, an electric lamp bulb, a hollow cylindrical metal shell serving as one contact of a contact base and afllxed to the lamp bulb by a ring of porous, insulating arc-quenching cem'ent near the rim of the shell, a fuse wire passing through said ring of cement and electrically connected to said shell and to a lamp bulb lead-in wire, part of the length of said fuse wire being directly embedded in the ocment through which it passes and anothert part being exposed to the atmosphere inside the base,

a second lead-in wire to said lamp bulb and elec.

form a tubular-like layer of insulation over the CPI inner surface of the shell to complete the insulation of the entire interior of the metal shell from the atmosphere inside the base by all paths except through the fuse.

4. The combination of claim 1, in which part only of the length of the fuse wire is embedded in the cement, another'part of the length being exposed to the atmosphere inside the base, and in which the fuse wire is of e metal consisting chiefly of nickel.

5. The combination of claim 11, n which a part only of the length of the fuse wire is embedded in the cement, another part of the length being exposed to the atmosphere inside the base,

in which the fuse wire is of a metal censist- 0 ing chiefly of nickel, end in which the cement is composed chiefly of marble flour and a resinoid.

6. The combination of claim 3, in which a part of the length of the fuse wire is embedded in the cement, another part of the length being exposed to the atmosphere inside the base, and in which the; fuse wire is of a metal consisting chiefly of nickel.

7. The combination of claim 3, in which a ROLLAND M. ZABEL. 

